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Molecular dynamics simulations are performed to study the influence of surface and fluid impurities on water–carbon interactions. In order to quantify these interactions we consider the canonical problem of wetting of a doped flat graphitic surface by a water system with impurities. As model fluid impurities we consider aqueous solutions of potassium–chloride with molar concentrations up to 1.8 M. Quantum chemistry calculations are performed to derive pair potentials for the ion–graphite interactions. The contact angle is found to decrease weakly with increasing ionic concentration, from 90° at 0 M to 81° at 1.8 M concentration. The influence of solid impurities is found to be more significant. Thus, 10, 15, and 20% coverages of chemisorbed hydrogen result in contact angles of 90°, 74° and 60°, respectively.